This invention relates generally to probe stations adapted for low current, low voltage parametric testing and measurement of discrete devices on silicon wafers.
More particularly, the invention relates to a probe station having improved geometry for multiple probe manipulators with Kelvin connections to the probe holders, and simplified connection systems for the triaxial cables guarding the probe holders and chucks supporting the silicon wafer.
The special requirements for parametric testing of semi-conductor wafers at low currents and low voltages are well known and discussed in many publications such as HP4284A Precision LCR Meter Operation Manual by Hewlett-Packard (December 1991); "Fixturing for Low-Current, Low-Voltage Parametric Testing" published in Evaluation Engineering (November 1990) by William Knauer; Japanese Laid-Open Patent Application No. H 2-220453 entitled "Equipment for On-Wafer Electronic Circuit Checking" laid-open Sep. 3, 1990 in the name of Y. Yamamoto, U.S. Pat. No. 5,345,170 issued Sep. 6, 1994 to Schwindt et al., and U.S. Pat. No. 5,457,398 issued Oct. 10, 1995 to Schwindt et al., these publications being merely illustrative of the prior art.
One known type of probe station for parametric measurement described in the aforementioned patents employs an octagonal box on top of a sealed enclosure, with supports for the probe holders and separate EMI shield tubes for the cables leading to the probe holders extending radially through sliding sealing members on the sides of the octagonal box. This arrangement requires cable connections to the probe holder to be made inside a rather congested area inside the octagonal box and requires two entry points into the octagonal box for each probe holder.
Accordingly, one object of the present invention is to provide an improved geometry for the probe holders and probe manipulators in a low voltage, low current parametric testing probe station.
Still another object of the invention is to provide improved EMI shielding and guarding of the device under test and associated cable and fixture elements.
Still another object of the invention is to provide an improved Kelvin connection system to the probe manipulators and guard members for multiple probing of a device under test.
Still another object of the invention is to provide improved probe holders with angular and longitudinal adjustment features.